1. Field
The described technology generally relates to an organic light-emitting display and a method of manufacturing the same, and more particularly, to an organic light-emitting display including a thin film transistor (TFT) and a method of manufacturing the organic light-emitting display.
2. Description of the Related Technology
In general, flat panel displays are classified into light-emitting type and light-receiving type. Light-emitting type displays may include flat cathode ray tubes, plasma display panels, electro luminescent devices, and light-emitting diodes. Light-receiving type displays may include liquid crystal displays (LCDs). Electro luminescent devices have desirable characteristics such as wide viewing angles, high contrast, and fast response speeds. The electroluminescent devices may be classified into inorganic and organic type according to a material used to form a light-emitting layer.
Organic electroluminescent devices are self-emissive and emit light by electrically exciting fluorescent organic compounds. They are considered as the next generation display that may address problems of LCDs because the devices have characteristics of low power consumption, a thin profile, wide viewing angles and fast response speeds.
The organic electroluminescent devices include a light-emission layer formed of an organic material between an anode electrode and a cathode electrode. As positive and negative voltages are applied respectively to the anode and cathode electrodes, holes injected from the anode electrode are moved to the light-emission layer through a hole transport layer (HTL) and electrons are injected from the cathode electrode and moved to the light-emission layer through an electron transport layer (ETL), and then, the holes and electrons are recombined in the light-emission layer to generate excitons.
As the excitons are changed from an excited state to a base state, fluorescent molecules in the light-emission layer emit light to form images. In a full-color type organic electroluminescent device, pixels that emit red (R), green (G), and blue (B) lights are formed to realize full-color images.
On the other hand, a thin film transistor (TFT) used in flat panel displays, such as the electroluminescent devices and LCDs, is used as a switching device for controlling operations of each of the pixels, or a driving device for driving the pixels. The TFT includes on a substrate a semiconductor active layer having a drain region and a source region doped with impurities of a high concentration, and a channel region between the drain and source regions, a gate insulating layer formed on the semiconductor active layer, and a gate electrode formed on an upper portion of the channel region of the semiconductor active layer.